import java.io.IOException;
import java.io.RandomAccessFile;
import java.net.HttpURLConnection;
import java.net.URL;
import org.omg.CORBA.portable.InputStream;
public class DownUtil {
public static void main(String[] args) throws Exception {
String path="https://ibaotu.com/sucai/18055535.html?clickFrom=colorsearch&kwd=gif??";
String target="11111";
int num=3;
DownUtil util=new DownUtil(path,target,num);
util.download();
}
private String path;
private String targetFile;
private int threadNum;
private DownThread[] threads;
private int fileSize;
public DownUtil(String path,String targetFile,int threadNum)
{
this.path=path;
this.threadNum = threadNum;
threads=new DownThread[threadNum];
this.targetFile = targetFile;
}
public void download() throws Exception
{
URL url = new URL(path);
HttpURLConnection conn=(HttpURLConnection)url.openConnection();
conn.setConnectTimeout(5*1000);
conn.setRequestMethod("GET");
conn.setRequestProperty("Accept","image/gif,image/jpeg,image/pjpeg,image/pjpeg,"
+"application/x-shockwave-flash,application/xaml+xml,"
+"application/vnd.ms-xpsdocument,application/x-ms-xbap,"
+"application/x-ms-application,application/vnd.ms-excel,"
+"application/vnd.ms-powerpoint,application/msword,*/*");
conn.setRequestProperty("Accept-Language","zh-CN");
conn.setRequestProperty("Charset","UTF-8");
conn.setRequestProperty("Connection","Keep-Alive");
fileSize = conn.getContentLength();
conn.disconnect();
int currentPartSize=fileSize/threadNum+1;
RandomAccessFile file = new RandomAccessFile(targetFile,"rw");
file.setLength(fileSize);
file.close();
for(int i=0;i<threadNum;i++)
{
int startPos = i*currentPartSize;
RandomAccessFile currentPart=new RandomAccessFile(targetFile,"rw");
currentPart.seek(startPos);
threads[i] = new DownThread(startPos,currentPartSize,currentPart);
threads[i].start();
}
}
public double getCompleteRate()
{
int sumSize=0;
for(int i=0;i<threadNum;i++)
{
sumSize+=threads[i].Length;
}
return sumSize*1.0/fileSize;
}
private class DownThread extends Thread
{
private int startPos;
private int currentPartSize;
private RandomAccessFile currentPart;
public int Length;
public DownThread(int startPos,int currentPartSize,RandomAccessFile currentPart)
{
this.startPos = startPos;
this.currentPartSize = currentPartSize;
this.currentPart = currentPart;
}
public void run()
{
try
{
URL url = new URL(path);
HttpURLConnection conn = (HttpURLConnection)url.openConnection();
conn.setConnectTimeout(5*1000);
conn.setRequestMethod("GET");
conn.setRequestProperty("Accept",
"image/gif,image/jpeg,image/pjpeg,image/pjpeg,"
+"application/x-shockwave-flash,application/xaml+xml,"
+"application/vnd.ms-xpsdocument,application/x-ms-xbap,"
+"application/x-ms-application,application/vnd.ms-excel,"
+"application/vnd.ms-powerpoint,application/msword,*/*");
conn.setRequestProperty("Accept-Language","zh-CN");
conn.setRequestProperty("Charset","UTF-8");
InputStream instream =(InputStream)conn.getInputStream();
instream.skip(this.startPos);
byte[] buffer = new byte[1024];
int hasRead=0;
while(Length<currentPartSize&&(hasRead=instream.read(buffer))!=-1)
{
currentPart.write(buffer,0,hasRead);
Length+=hasRead;
}
currentPart.close();
instream.close();
}
catch(IOException e)
{
e.printStackTrace();
}
}
}
}
编译正常,执行时出现
Exception in thread "main" java.io.IOException: 试图将文件指针移到文件开头之前。
at java.io.RandomAccessFile.setLength(Native Method)
at DownUtil.download(DownUtil.java:73)
at DownUtil.main(DownUtil.java:18)
谢谢解决一下,刚学》